It appears we can only guess what is being said in the enquiry, as it is being held in private. Stories in most of the press are thus also just speculation.
Folk seem eager to believe in software demons in an increasingly automated, software driven world.
We should note the question is on the safety of the whole aircraft, not just the software.
As said, even though some certification duties are outsourced to Boeing employees, the MCAS software itself will still have gone through all of the same development processes as required by the standard.
The design and testing of the overall aircraft as a system seems more of a concern. That is where I would expect the investigation to focus.